Add some capability for setting the Vary response field when
	mod_rewrite makes changes based upon request fields.  This is
	by no means a complete treatment of the problem (redirects don't
	inherit the Vary at the moment, for instance), but at least
	we're not ignoring Vary here completely any more.

PR:		1644
Reviewed by:	Ralf Engelschall


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@81811 13f79535-47bb-0310-9956-ffa450edef68